Coupling assemblies that convert rotation movement into an axial movement, can serve as so-called hang-on couplings for optionally driving an additional driving axle or as locking couplings at a transmission stage for the variable distribution of torque between two driving axles of a differential gear.
From DE 39 20 861 A1 there is known a mechanical axial setting device for actuating a friction coupling in a locking differential, which axial setting device is provided in the form of a ball ramp assembly. This prior art axial setting device comprises an axially fixed supporting ring and an axially displaceable setting ring of which one is rotatable relative to the other one. For rotating purposes, there is provided a rotary drive in the form of an electric motor which is able to drive the rotatable ring via a reduction stage.
DE 10 2005 053 555 B3 proposes a ball ramp assembly which is controlled by an electric motor and which serves to actuate a friction coupling in a differential gearbox with a variable torque distribution. In the axial setting devices of this type, actuation is effected by an electric motor which achieves a relative rotation of the two rings. The electric motor must have sufficiently large dimensions in order to provide the torque capacity required for rotational purposes, the result being that the electric motors require a great deal of space and in view of the so-called packaging, such that they may be difficult to be integrated into the unit which is actuated by the axial setting device.
From DE 103 49 030 A1 there is also known a hydraulic axial setting device with a pump and a piston for loading a friction coupling.
DE 10 2005 018 907 A1 proposes a differential gearbox with a disc brake for an electrically driven driving axle. The brake can be actuated via a ball ramp, and the rotation of a rotatable component of the ball ramp can be effected by a hydraulic cylinder.
From DE 36 17 074 A1 there is known an axle assembly for a motor vehicle which comprises a differential gear, a brake which acts on the half-shafts of the differential gear and a differential lock. Between the brake and the differential lock there is provided a common actuating device which is provided in the form of a ball ramp device and comprises two pressure plates. For rotating one of the two pressure plates relative to the other pressure plate, there is provided a hydraulic cylinder.
AT 004 635 U1 proposes a claw coupling for a lockable axial differential. The claw coupling is actuated by an actuating device comprising two rings of which one is rotatable relative to the other one. For rotating the first ring relative to the second ring, there is provided an actuator provided in form of a solenoid.